Hidalgo said authorities could potentially fine each illegal property 12,500 Euros ($14,240) each. Owners are required to register their Airbnb properties with local authorities, and must display the registration number in the listing.

Whatever the fine may be, it might just be drop in the ocean for Airbnb, which in the third quarter of 2018 recorded more than $1 billion in revenue, and is on track to be profitable for the second year in a row.